[20.04] Boot hangs at "loading initial ramdisk"

[zskdan]

My XPS 15 9550 hang at "loading initial ramdisk" after upgrade from 18.04 to 20.04. Tried some workarounds described https://bugs.launchpad.net/ubuntu/+source/intel-microcode/+bug/1853369 but no success! (downgranding grub, and intel-microcode).

[Alex Murray (alexmurray)]

Can you please try editing the grub command-line during boot and adding

dis_ucode_ldr

as an extra kernel boot parameter?

If this allows the machine to boot then it shows the issue is specific to the microcode but if not then this is likely a kernel issue - also given that we ship the same microcode in all releases I suspect that this is likely a kernel issue but it would be good to confirm this. If this does turn out to look like a kernel issue then this bug should be reassigned against the linux package.

[zskdan (zelqotbi)]

Thanks @Alex for your reply. So Yes I confirm that is not a microcode issue as I was not able to boot with dis_ucode_ldr extra kernel param.
Sorry for the noise I'll assign it then to the kernel.

[zskdan (zelqotbi)]

I did more experimentations, and found out:

0. Official 18.04.5 Ubuntu Desktop images flashed on USB stick booted perfectly.
1. Official 20.04.2 and 21.04 Ubuntu Desktop images flashed on USB stick, does not boot (only black screen).
2. Installing an OEM kernel (linux-image-5.10.0-1029-oem) does not fix the issue either.
3. Installing a generic kernel (ex: linux-image-5.4.0-74-generic) without **modules-extra** package makes my system boot up (but with some drawbacks: no wifi, no bluetooth, ...)

[zskdan (zelqotbi)]

If I keep an initrd image of a kernel before installing the "modules-extra" I got finally my system to boot and to work perfectly.

$ sudo cp /boot/initrd.img-5.4.0-74-generic /boot/initrd.img-5.4.0-74-generic.wo.extras
$ sudo apt install linux-modules-extra-5.4.0-74-generic
$ sudo mv /boot/initrd.img-5.4.0-74-generic /boot/initrd.img-5.4.0-74-generic.extras
$ sudo ln -s initrd.img-5.4.0-74-generic.wo.extra /boot/initrd.img-5.4.0-74-generic

So, I think that the issue comes from the "modules-extra" package.